超强陶瓷焊接结构和变形机制

4^th国际会议和博览会在陶瓷和复合材料

,2018年5月14日至15日|罗马,意大利

Ghatu Subhash

美国佛罗里达大学

主题:启J垫。Sci >

DOI:10.4172 / 2321 - 6212 c1 - 013

文摘

Ultrahard陶瓷主要源于两种结构形式:类金刚石和二十面体。而类金刚石结构(例如,天然钻石和c-BN)的显微硬度记录超过100 GPa,二十面体boron-rich固体近年来引起了相当大的关注由于其强烈的热/化学稳定性和极佳的高硬度(~ 40 GPa)和低质量密度(~ 2.5克/立方厘米)。碳化硼(B4C)和一氧化二硼(B6O)是两种受欢迎的陶瓷这类材料和首选的候选人的影响和耐磨性应用程序。虽然其结构主要由12原子二十面体和几个原子债券二十面体,这些原子的排列及其化学性质控制其变形机制。例如,B4C 3-atom链连接到赤道二十面体的原子,B6O没有链,但一个氧原子结合二十面体的两侧。由于亲密在硼和碳原子半径,B4C展品多态性,碳可以代替硼和潜在产量超过200多晶型物。另一方面,B6O没有多晶型物。因此B6O比B4C结构更加均匀。这些结构上的差异影响它们的属性和变形机制。两种材料硬度高(> 30 GPa),低密度(2.52克/立方厘米B6O B4C和2.6克/立方厘米),抗压强度高(GPa) 5、温和的断裂韧性(3.4 MPa·m1/2 B4C和4.2 MPa·m1/2 B6O)和展览无定形化(本地化的晶体结构崩溃)在高压负载。 But, amorphization in B4C can be detected in Raman spectroscopy (through appearance peaks beyond 1200 cm-1), B6O does not show any new peaks due to amorphization. While the 3-atom chain bending has been proposed as the main mechanism for amorphization in B4C, the lack of chain structure in B6O raises new questions as the root-cause of amorphization in this material. Similarly, B4C has been found to occasionally undergo deformation twinning but B6O has been shown to undergo ‘nanotwinning’ (twin spacing of nm scale) even in virgin state and has been theorized to provide extremely high hardness if the entire specimen undergoes nanotwinning at critical twin spacing of two atomic planes. In this research, a coordinated experimental, spectroscopic, microscopic, and quantum mechanical investigations are performed to provide fundamental insight into the above issues. Finally, implications of these structural, behavioral and bonding differences during high pressure dynamic deformation will be discussed. The long-term goal of this research is to identify novel avenues for designing of ultrahard materials with tailored properties.

传记

Ghatu Subhash进行交叉的多学科研究固体力学,材料科学,生物力学。Subhash的研究导致了披露和临时专利发明新方法快速灵活的测试包封,影响吸收垫防止头部受伤,UO2燃料的快速处理,和发展的超强碳化硼众多应用程序作为盔甲,硬磨料和热电。电子邮件:(电子邮件保护)

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